The detection and diagnosis of fractures in teeth is a difficult but very common clinical problem that has been specifically identified as a top research priority by the American Association of Endodontists Foundation. Currently, dentists use patient history, visual examination, comprehensive endodontic examination and radiography to diagnose cracked teeth. However, clinical signs and symptoms are highly variable and are often insufficient to reach a precise diagnosis; signs and symptoms associated with cracks are also associated with other very common diagnoses. Although presence of a visible fracture line in enamel and a high ratio of restoration to total natural crown volume are associated with an increased incidence of tooth fracture, this finding applies to a patient population, not to the diagnosis of cracks in individual patients. Dental radiographs or cone beam computed tomographs generally do not show hairline cracks themselves until some separation has occurred, only subsequent bony damage following bacterial colonization and inflammation or infection. An inexpensive, portable, non-invasive, non-ionizing method of identifying cracks would have significant therapeutic value. Accurate diagnosis would allow selection of appropriate interventions: none, monitoring, root canal treatment and/or coronal coverage, or extraction. Our approach is to use ultrasound as a non-invasive imaging tool for the detection of fractures in teeth. Ultrasound is highly effective in detecting physical discontinuities such as fractures or detached restorations, even if such discontinuities are smaller than the acoustic wavelength. Ultrasound also has the ability to penetrate most hard structures, including restorations - a task that is difficult for radiography. Therefore, ultrasonography may provide a significant benefit to patients by allowing early detection of tooth defects as well as treatment planning, avoiding under- or over- or inappropriate treatment. An additional benefit of ultrasound is that it is inherently non-ionizing, thereby avoiding the health risks associated with radiography. The proposed novel probe design will efficiently couple ultrasound energy directly into the tooth, and will be capable of imaging surface and sub-surface features within the tooth, including fractures, caries, and the boundaries of the pulp chamber. This proposal will focus on tooth fractures; however, the probe will be designed for volumetric imaging of the whole tooth. The focus of this Phase I SBIR effort is to design and integrate a customized ultrasound probe for imaging of tooth fractures, and to demonstrate technical feasibility through in vitro and ex vivo studies.